journeyquest

My 90 CRX DX lost compression in one cylinder and the mechanic says it is a burnt valve. Would this be caused by carbon? The car has 90,000 miles. Is it worth fixing? It was running rich. I think it was dumping raw fuel into the exhaust and ruined my cat. Thanks.

4drEF

That's a personal opinion if it's worth fixing.
You may be able to find an entire used motor for much less than the valve fix is going to cost you.
The DX motor is usually kicked to the curb when people do an engine swap.

If you do decide to fix it, it will require the cylinder head to be pulled. If you aren't doing the work yourself then this is going to cost $$$
At minimum you will have to replace the headgasket and valve cover seals - and while you are are at it you will have open access to the timing belt and water pump.
The actual valve is inexpensive, but all the parts and labor required to get to it add up fast.

journeyquest

I have a new cat, timing belt, water pump, tensioner, oil, filter and spark plugs. So that should cut back on cost. The car is automatic so i dont see putting a hotter engine in it. This is just transpo to save money on gas. I have a couple chevy v8 gas hogs already. I can pull the head and install it, but not sure about machine work? Or what other problems lurk under the head, if any?

Julio@Bisimoto

Seems kind of strange to be a burnt valve with that kind of miles on it. Did your mechaninc do a compression test or leak down test. If he didnt do a leak down have your him try that first and see if it is leaking from intake or exhaust valves or from the piston rings. Even might be a good idea to decarbonise the engine with a top engine clean and check valve lash before tearing down the engine.